Integration of optically active and diamond-based color centers with semiconductor substrates for quantum devices

Abstract

Methods for fabricating optically active quantum memories into quantum-grade diamond thin films and then bonding them to semiconductor substrates are described. Semiconductor substrates are optically and electronically functionalized in preparation for using a flip-chip bonding technique to bond the functionalized substrates to overgrown diamond thin films that host color centers. By purposefully growing quantum-grade diamond thin films and implanting them with color centers separately from fabrication processes that functionalize the substrates, the high quality, purity, and crystallinity of the thin films are preserved, while also allowing for further customization of the types of color centers that are implanted into the diamond.

What is claimed is: 
     
         1 . A method for fabricating optically active quantum memories, the method comprising:
 depositing overgrown diamond thin film layers onto top surfaces of corresponding diamond substrates;   etching alignment markers into top surfaces of the overgrown diamond thin film layers;   implanting silicon ions into the top surfaces of the overgrown diamond thin film layers, wherein the implanting is localized by referencing the alignment markers;   performing flip-chip bonding, wherein the performing the flip-chip bonding comprises bonding, using a deposited bonding layer as an intermediary layer, the top surfaces of the overgrown diamond thin film layers and a top surface of a separate semiconductor substrate to one another;   removing the diamond substrates; and   etching thru-holes into the top surfaces of the overgrown diamond thin film layers and proximate to the implanted silicon ions, wherein:
 the etching is localized by referencing the alignment markers; and 
 the implanted silicon ions and the thru-holes form the optically active quantum memories. 
   
     
     
         2 . The method of  claim 1 , wherein:
 the method further comprises patterning additional alignment markers onto the top surface of the separate semiconductor substrate; and   the performing the flip-chip bonding further comprises aligning the alignment markers on the top surfaces of the overgrown diamond thin film layers to the additional alignment markers on the top surface of the separate semiconductor substrate.   
     
     
         3 . The method of  claim 2 , wherein the aligning the alignment markers on the top surfaces of the overgrown diamond thin film layers to the additional alignment markers on the top surface of the separate semiconductor substrate is a passive alignment that is completed using an optical-based alignment. 
     
     
         4 . The method of  claim 1 , further comprising:
 determining a concentration of additional ions to implant into the overgrown diamond thin film layers in order to tune an optical or electrical property of the optically active quantum memories; and   implanting the additional ions, at the determined concentration, into the overgrown diamond thin film layers.   
     
     
         5 . The method of  claim 1 , further comprising:
 determining a concentration of gas to emit during the depositing the overgrown diamond thin film layers in order to tune an optical or electrical property of the optically active quantum memories; and   emitting the concentration of the gas during the depositing the overgrown diamond thin film layers.   
     
     
         6 . The method of  claim 1 , wherein the implanting the silicon ions into the top surfaces of the overgrown diamond thin film layers comprises:
 depositing a resist layer onto the top surfaces of the overgrown diamond thin film layers;   etching nano-apertures into the resist layer, based on referencing the alignment markers, such that portions of the top surfaces of the overgrown diamond thin film layers are exposed while other portions of the top surfaces of the overgrown diamond thin film layers remain covered by the resist layer;   uniformly implanting the silicon ions; and   removing the resist layer.   
     
     
         7 . The method of  claim 1 , wherein the implanting the silicon ions onto the top surfaces of the overgrown diamond thin film layers comprises:
 determining intended locations of silicon vacancies based on referencing the alignment markers; and   implanting the silicon ions using a focused ion beam implantation.   
     
     
         8 . The method of  claim 1 , further comprising:
 prior to the depositing the overgrown diamond thin film layers,
 determining, based on intended optical properties of the optically active quantum memories, a given miscut angle to cut the top surfaces of the corresponding diamond substrates along; and 
 cutting the top surfaces of the corresponding diamond substrates along the given miscut angle. 
   
     
     
         9 . The method of  claim 1 , wherein the depositing the overgrown diamond thin film layers is performed using chemical vapor deposition. 
     
     
         10 . The method of  claim 9 , further comprising:
 determining temperature and electrical field conditions that are to be used during the depositing, via chemical vapor deposition, the overgrown diamond thin film layers based on intended optical properties of the optically active quantum memories; and   applying the determined temperature and electrical field conditions during the depositing.   
     
     
         11 . The method of  claim 1 , further comprising:
 prior to the etching the thru-holes, uniformly etching a portion of the overgrown diamond thin film layers, wherein the etched portion is determined based on intended optical properties of the optically active quantum memories.   
     
     
         12 . The method of  claim 1 , wherein a localization of the etching the thru-holes comprises use of Electron-beam lithography and a reference to additional alignment markers that have been patterned onto the top surface of the separate semiconductor substrate. 
     
     
         13 . The method of  claim 1 , wherein the separate semiconductor substrate is made from one or more of the following:
 silicon;   silicon nitride;   silicon oxide;   lithium niobate;   aluminum nitride;   aluminum oxide; or   gallium arsenide.   
     
     
         14 . The method of  claim 1 , wherein the deposited bonding layer is made from one of the following:
 silicon oxide;   aluminum oxide;   copper;   aluminum; or   gold.   
     
     
         15 . A method for fabricating quantum devices, the method comprising:
 receiving a set of three-dimensional stacks, comprising overgrown diamond thin film layers that have been grown onto top surfaces of corresponding diamond substrates;   etching alignment markers into top surfaces of the overgrown diamond thin film layers;   implanting ions into the top surfaces of the overgrown diamond thin film layers, wherein the implanting is localized by referencing the alignment markers;   receiving a semiconductor substrate;   patterning additional alignment markers onto a top surface of the semiconductor substrate;   performing flip-chip bonding, wherein the performing the flip-chip bonding comprises:
 aligning the alignment markers on the top surfaces of the overgrown diamond thin film layers to the additional alignment markers on the top surface of the semiconductor substrate; and 
 bonding, using a deposited bonding layer as an intermediary layer, the top surfaces of the overgrown diamond thin film layers and a top surface of a separate semiconductor substrate to one another; 
   removing the diamond substrates; and   etching thru-holes into the top surfaces of the overgrown diamond thin film layers and proximate to the implanted ions, wherein:
 the etching is localized by referencing some combination of the alignment markers and the additional alignment markers; and 
 the implanted ions and the thru-holes form the quantum devices. 
   
     
     
         16 . The method of  claim 15 , wherein the deposited bonding layer is made from one of the following:
 silicon oxide;   aluminum oxide;   copper;   aluminum; or   gold.   
     
     
         17 . The method of  claim 15 , further comprising:
 prior to the etching the thru-holes, uniformly etching a portion of the top surfaces of the overgrown diamond thin film layers, wherein the etched portion is determined based on intended optical properties of the quantum devices.   
     
     
         18 . The method of  claim 15 , wherein a localization of the etching the thru-holes comprises use of Electron-beam lithography or optical lithography and a reference to additional alignment markers that have been patterned onto the top surface of the separate semiconductor substrate. 
     
     
         19 . A method for fabricating optically active quantum memories, the method comprising:
 depositing, via chemical vapor deposition, overgrown diamond thin film layers onto top surfaces of corresponding diamond substrates, wherein gaps between respective ones of the overgrown diamond thin film layers within a chemical vapor deposition chamber are determined to ensure uniformity of deposition of the overgrown diamond thin film layers with respect to one another;   implanting silicon ions into portions of the top surfaces of the overgrown diamond thin film layers;   performing flip-chip bonding, wherein the performing the flip-chip bonding comprises bonding, using a deposited bonding layer as an intermediary layer, the top surfaces of the overgrown diamond thin film layers and a top surface of a separate semiconductor substrate to one another;   removing the diamond substrates; and   etching thru-holes into the top surfaces of the overgrown diamond thin film layers and proximate to the implanted silicon ions, wherein the implanted silicon ions and the thru-holes form the optically active quantum memories.   
     
     
         20 . The method of  claim 19 , further comprising:
 determining temperature and electrical field conditions that are to be used during the depositing, via the chemical vapor deposition, the overgrown diamond thin film layers based on intended optical properties of the optically active quantum memories; and   applying the determined temperature and electrical field conditions during the depositing.